1. Field of the Invention
The present invention relates to a resin molding machine in which a molding material, such as a thermoplastic resin and a thermosetting resin, is fed from a sprue, through a gate, into a cavity for producing a resin molded article, such as an electronic component.
2. Description of the Related Art
This type of resin molding machine generally uses a three-plate pinpoint-gate mold.
In this mold, as shown in FIGS. 11 and 12, a cavity 53 is provided between the upper surface of a stationary lower mold 51 and the lower surface of a movable upper mold 52 moves vertically between open and closed positions of the mold. The upper mold 52 includes a runner 55 and a gate 54 communicating with the cavity 53. A sprue bushing 56a, which vertically moves and includes a sprue communicating with the runner 55, is disposed on the upper surface of the upper mold 52.
To produce a resin molded article using the above-described resin molding machine, a molding material (see the arrow) is fed, with the mold closed, from the sprue 56, through the runner 55, past the gate 54, and into the cavity 53.
Subsequently, the gate 54 is cut by opening the mold, a resin molded article 58 in the cavity 53 is ejected, and residual material 59 remaining in the gate 54, the runner 55, and the sprue 56 is removed.
A known method for removing this residual material 59 is to provide a residual-material remover 60, as shown in FIGS. 13 and 14, separately from the resin molding machine.
In this residual-material remover 60, a main body 61 supports an arm 62 movably in upward and downward directions and forward and backward directions as indicated by the arrow in FIG. 14. A pinching member 63 having a pair of nails 63a is attached to the tip of the arm 62.
The residual material 59 is held by a runner locking pin 57a as the gate 54 is cut by opening the mold.
Subsequently, the arm 62 moves forward to pinch a sprue section 59a of the residual material 59 with the pinching member 63. The arm 62 is then lowered and moved backward, while extracting the residual material 59 from the sprue bushing 56a, to transfer the extracted residual material 59 to a residual-material container.
A residual-material remover provided separately from a resin molding machine, such as that described above, requires a driving mechanism for driving the arm to move horizontally and vertically. This increases costs.
Moreover, to extract the above-described residual material, the arm movement requires switching of the direction from forward and backward movement to upward and downward movement. In addition, the extent to which the mold opens must correspond to the upward and downward distance of the arm movement. This adjustment increases the time for opening the mold, and thus, increases the cycle time.
Moreover, to reliably hold the residual material with the pinching member, for example, the thickness of the sprue section of the residual material must be increased. Such a requirement results in an increased amount of residual material.